May 4, 1999
Researchers develop simple test for detection of deadly cancer
Toronto– A team of Toronto researchers has developed a simple test that promises to significantly reduce mortality rates for a deadly form of cancer. The research is published in the May issue of the Journal of the National Cancer Institute, the leading journal in the cancer research field.
Researchers at The Hospital for Sick Children (SickKids), Mount Sinai Hospital, Toronto Hospital, the University of Toronto and the Rouge Valley Health system’s Centenary Site, have completed a clinical trial of a new strategy for the detection of nasopharyngeal cancer (NPC), a tumour that grows deep behind the nose.
NPC is the major cause of death from cancer in Hong Kong, southern China and several Pacific and Mediterranean rim countries. Most North American patients who develop this cancer are of Asian, Mediterranean or African descent. In Canada, Chinese immigrants, Jews and Inuit belong to high-risk groups.
"Usually this type of cancer is detected only very late in its progress because of its obscure location in the body and he lack of signs and symptoms," says Dr. Jeremy Freeman, Temmy Latner/Dynacare Chair in Head and Neck Oncology and an Otolaryngologist at Mount Sinai Hospital, and a professor of Otolaryngology at the University of Toronto. "Currently, prognosis for patients is often late. However, the diagnostic test we have developed can be administered by an ear-nose and throat (ENT) or general physician on a routine basis and represents a true breakthrough because it detects the cancer at an early stage and allows us to act more proactively."
"In this cancer, every single tumour cell carries Epstein-Barr virus and we believe that the virus plays a direct role in tumour development," says principle investigator Dr. Michael Dosch, a senior scientist at The Hospital for Sick Children and a Professor of Paediatrics at U of T. "We have now learned to use this relationship to detect the tumour by tracing the virus."
The Toronto team developed an ambulatory testing technique using a sheathed brush reminiscent of a pap smear brush. Cells are gently retrieved from the back of the nose where the tumour develops. The cells are then analyzed for Epstein-Barr virus with a gene-based test. The test has an accuracy rate of over 90 percent. The presence of the virus gene is a strong predictor of the cancer.
The seven-year study evaluated subjects from the Toronto area that had either established or suspected NPC (21 patients), while 96 other patients had minor otolaryngological complaints, and 53 had head and neck cancers other than NPC. Thirty-two addition patients had been treated for NPC. Eighty-six percent of NPC patients were of Asian descent.
"The next stage in this exciting development will be to conduct a large population-based screening test in some of the high risk groups such as Chinese immigrants in Toronto," explains Dr. Raymond Ng, an otolaryngologist at the Centenary site of the Rouge Valley Health System. "This early screening test will help us identify patients with no overt clinical symptoms. The benefits of treating the disease early and the long-term cost savings for the Canadian health care system will be substantial."
In addition to Drs. Dosch, Freeman and Ng, the research team included Cathryn Tune, Per-Gunnar Liavaag and Roy Cheung of The Hospital for Sick Children; Michael van den Brekel, Thomas Shpitzer and Jeroen Kerrebijn of Mount Sinai Hospital; Dr. John Irish of the Toronto Hospital; and Dr. David Payne of Princess Margaret Hospital.
The research was supported by funds from the Medical Research Council of Canada, Temmy Latner/Dynacare, The Saul A. Silverman Family Foundation, the Tauba and Solomon Spiro Family Foundation as an Isabel Silverman Canada-International Scientific Exchange Program Project, and The Hospital for Sick Children Foundation.
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